In Excel I can add the following formula...
=IF(A1="", "", IF(B1="", NOW(), B1))
This formula says when a value in added to cell A1 populate cell B1 with the current date. To get this to work you must turn on an Excel feature named iterative calculation (Options==>Formulas==>Enable iterative calculation).
I use this when I'm building an Excel task journal and I want to auto-populate the date.
The important thing about this formula is that the date value is not updated if another change is made.
In Numbers, how can I auto populate a date value in column "B" when a value is set in column "A"? It's important to keep in mind that once the date is set I don't want it to change.
Here is my attempt at translating this formula in Apple Numbers.
=IF(A2="", "", IF(B2="", NOW(), B2))
I get an error message.
This formula can't reference its own cell, or depend on another formula that references this cell